Bettina represents one set of values for Parvez and an entirely different set for Ali. Her role in the story is established within this clash of values.
For Parvez, Bettina represents a confirmation of what makes sense and what is right. From a personal point of view, Bettina operates as a confidante. Parvez "could talk to her about things he'd never be able to discuss with his own wife." Bettina also represents the liberal tolerance of England that Parvez embraces. When he tells her that he is going to evict Ali from him home, Bettina speaks words of liberal understanding: "But you mustn't give up on him... Many young people fall into cults and superstitious groups. It doesn't mean they'll always feel the same way."
Parvez's liberal understanding is evident when he tells his son that since they are in England, they must strive to assimilate. Bettina echoes this cultural assimilation with her calls for communication between the two, suggesting to Parvez that he speak of his "philosophy of life" with Ali. In many ways, Bettina confirms Parvez's own understanding of what to do and how to live. The reason he talks with her so much is because he knows he will receive words that confirm his world view. Her pluralist and tolerant outlook is evident when she insists on talking to Ali in the cab. She communicates the understanding that Parvez believes and wants to convey, but stammers in doing so.
The fact that Bettina represents Parvez's own belief system is in large part why Ali finds her repugnant. The cab exchange between both of them reveals what she represents to Ali. The initial impressions Kurieshi describes as Ali enters the cab contain the materialist, soulless, and decadent Western culture that the son has declared as his enemy: "Bettina's short skirt, gaudy rings and ice-blue eyeshadow... the smell of her perfume."
In contrast to his father, Ali believes in a very narrow worldview. In Ali's mind, Bettina is an outsider. Her presence is a challenge to his cultural, social, and gender- constructed values. This is evident when he repels her questions about his schooling with "Who are you to ask me these questions?" Finally, when he affirms that his father could not love him if he allows "a woman like you to touch him like that," it is clear that Bettina represents everything that Ali detests. Bettina and the effect she has on men like Parvez represent what Ali is fighting against.
Bettina's role is to operate as an intermediary between both men. Parvez struggles with showing understanding because of the complex emotions he feels toward his son. Bettina's role is to enable his tolerance to emerge through her advice and insight.
At the same time, her role is also to spark the final blowup between father and son. Once Ali abuses her in such a brutal manner and she leaves, it is clear that Parvez's liberal understanding leaves with her. Ali's treatment of her enables him to become the very fanatic he fears his son is becoming.